This invention relates to a process for the simultaneous drying and granulation of water-containing monoglyceride (ether) sulfate pastes using a thin-layer evaporator.
Monoglyceride (ether) sulfates are distinguished by excellent detergent properties and high ecotoxicological compatibility. For this reason, these anionic surfactants are acquiring increasing significance. Although, hitherto, they have generally been used in liquid formulations, for example dishwashing detergents or hair shampoos, there has also been a market demand in the meantime for solid water-free formulations which can be incorporated, for example, in washing powders, toothpastes or syndet soaps.
On an industrial scale, liquid surfactant formulations are generally dried by conventional spray drying where the aqueous surfactant paste is sprayed at the head of a tower in the form of fine droplets which meet hot drying gases flowing in countercurrent. However, the drastic conditions involved often lead to hydrolysis phenomena, unwanted discoloration of the products, deposits on the walls of the spray drying towers and, hence, to impurities in the spray-dried material in the form of carbonized residues. In addition, the necessary cleaning of the towers results in down times which occasionally make the process expensive. Another problem is that conventional processes do not lead to the particularly preferred heavy powders with a bulk density above 500 g/l and, at the same time, a greatly reduced dust content. However, it is precisely these two parameters which are of considerable importance for economic, performance and safety reasons.
DE-A1 42 09 339 (Henkel) describes a process a process for the production of free-flowing detergent granules in which drying is carried out in turbo dryers, i.e. in horizontally mounted cylindrical dryers with rotating internals. Detergent pastes containing monoglyceride sulfates can also be dried in this way. In addition, powder-form monoglyceride sulfates are also mentioned in DE-PS 725 474.
Accordingly, the complex problem addressed by the present invention was to convert water-containing monoglyceride (ether) sulfate pastes with minimal outlay on equipment and without using inorganic or organic carriers into substantially water-free and dust-free granules which would be distinguished by acceptable color quality, a high bulk density, good flow properties, satisfactory stability in storage and, in comparison with known products, by at least comparable performance properties.